nimble Apache NimBLE (BLE host-layer) for NuttX

This application will build nimBLE stack (host-only) as a library/application in NuttX.

For a Central/Peripheral example that tests connections, GATT service discovery, and subscriptions without Bluetooth hardware, see Testing Bluetooth without hardware.

Configuration

NimBLE needs CONFIG_NET_BLUETOOTH and a Bluetooth controller exposed through the NuttX HCI socket, and conflicts with the NuttX host (CONFIG_WIRELESS_BLUETOOTH_HOST must be off). Enable the GAP roles the application needs with CONFIG_NIMBLE_ROLE_*.

Cryptography uses Mbed TLS (CONFIG_MBEDTLS_MINIMAL is enabled by default). CONFIG_NIMBLE_TINYCRYPT builds the legacy bundled TinyCrypt instead.

CONFIG_NIMBLE_EVENTQ_SIZE sets the depth of the host event queue. Hosts that scan need room for the advertising reports queued by the transport; the default is 16, or 32 with mesh.

Bluetooth Mesh

CONFIG_NIMBLE_MESH builds the NimBLE mesh stack. Provisioning bearers and node features:

  • CONFIG_NIMBLE_MESH_PB_ADV - PB-ADV, needs the broadcaster and observer roles.

  • CONFIG_NIMBLE_MESH_PB_GATT - PB-GATT, needs the peripheral role.

  • CONFIG_NIMBLE_MESH_GATT_PROXY, CONFIG_NIMBLE_MESH_RELAY, CONFIG_NIMBLE_MESH_FRIEND, CONFIG_NIMBLE_MESH_LOW_POWER, CONFIG_NIMBLE_MESH_PROVISIONER.

  • CONFIG_NIMBLE_MESH_DEVICE_NAME - name in the PB-GATT and proxy scan response.

Resource limits: CONFIG_NIMBLE_MESH_SUBNET_COUNT, CONFIG_NIMBLE_MESH_APP_KEY_COUNT, CONFIG_NIMBLE_MESH_MODEL_KEY_COUNT, CONFIG_NIMBLE_MESH_MODEL_GROUP_COUNT, CONFIG_NIMBLE_MESH_ADV_BUF_COUNT, CONFIG_NIMBLE_MESH_TX_SEG_MAX and CONFIG_NIMBLE_MESH_RX_SEG_MAX.

A mesh node scans continuously and the host is busy for up to a second during provisioning (ECDH), so the Bluetooth socket must absorb a burst of advertising reports: set CONFIG_NET_BLUETOOTH_BACKLOG=32 and CONFIG_IOB_NBUFFERS=64. With the defaults (8 and 8) the socket drops the oldest queued HCI event, which can be a Command Complete, and the host resets on an HCI timeout.

The controller must support scanning and advertising at the same time. With the nRF52 SoftDevice Controller the peripheral-only configuration has no scanning, so mesh needs CONFIG_NRF52_SDC_MULTIROLE and CONFIG_BLUETOOTH_MAX_CONN=2 (one peripheral plus one central role).

Mesh applications create the HCI socket task, register the mesh GATT services with bt_mesh_register_gatt() before the host starts, call bt_mesh_init() from the host sync callback, run mesh_adv_thread() on its own thread and enable provisioning with bt_mesh_prov_enable(). See the node, sensor and vendor examples.

Nodes can be provisioned from Linux with BlueZ bluetooth-meshd and mesh-cfgclient. meshd needs exclusive access to the adapter, so bluetoothd must not manage it at the same time.

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